It is known to provide two or more compressors to be connected in parallel to a single refrigeration system and to cycle off or on a compressor while another compressor continues to run to provide variable capacity for the system. However, such systems have problems involved when a cycled-off compressor is turned on to start running while another compressor is at that time running in the system to create a system pressure against which the starting compressor must start. Also, if any of the multiple compressors are of the part unloading multiple cylinder hermetic shell type, the maximum saturated discharge temperature for safe operation of the part unloaded running compressor will be lower than when the compressor is running fully loaded because of the work done on and the heating of the recirculating refrigerant gas in the shell of the part unloaded compressor. In a multiple compressor system, this means that the upper limit of saturated gas discharge temperature will be lower than would be possible if no part unloading compressors were to be in operation. It is believed desirable to have the safe upper limit of saturated gas discharge temperature to be as high as possible for any given step capacity condition of operation of the system. According to this invention, a first one of the hermetic shell compressors is a multicylinder part unloading compressor to be always running either fully loaded or part unloaded when the system operates and the second hermetic shell compressor which is to be cycled off or on is connected to the system with its inlet suction line connected through the shell of the first compressor so that when the first compressor is running in part unloaded condition, the recirculating gas in its shell will be mixed with and drawn into the shell of the second compressor, when running, enabling the safe saturated gas upper temperature limit for the discharge gas from either compressor to be higher than could be possible if the suction inlet for the second compressor was not connected to the system through the shell of the first compressor.